Toners containing a crystalline polyester as a resin binder have been studied for the purpose of improving low-temperature fixing ability, which is one of the major problems to be solved in electrophotography (JP 2001-222138 A). However, further improvement is still highly desired in properties which is incompatible with low-temperature fixing ability, for example, in storage property as well as durability such as prevention of toner spent to carrier in the two-component development or durability such as prevention of toner fusion onto the blade in the monocomponent development.
In order to improve the properties including durability, there is proposed a high molecular weight-type crystalline polyester having a molecular weight distribution shifted to the higher side (JP 2004-61875 A). However, when a toner containing a crystalline polyester is used for a continuous printing in a high-speed printer, especially in a high-speed printer at a linear speed exceeding 370 mm/sec, a problem of image quality deterioration called as “ghost phenomenon” is likely to arise. The “ghost phenomenon” is a phenomenon that a toner is developed even on a portion where a toner is not developed in a normal operation (non-image bearing portion) upon applying the bias voltage, by reason that the photoconductor surface becomes deteriorated during the course of a continuous printing, resulting in no surface potential on the surface.